Warm and cold climatic spells in the Arctic, over the past 1000 years, imprinted on India’s monsoon fluctuations during that period, a climate reconstruction study finds.
Warm Arctic conditions were linked to intense rainfall over the Indian subcontinent while cold conditions in the Arctic were associated with weak spells of rain over the Indian subcontinent over the past 1000 years, say scientists at India’s National Centre for Polar and Ocean Research (NCPOR).
In collaboration with Norwegian counterparts, they reconstructed the past climate history from the Arctic region that’s warming faster than any other place on the planet. The scientists say the Arctic’s influence on the short-term changes in the Indian monsoon may become more pronounced as the region experiences further warming due to human actions.
“Large Arctic variabilities (greater than 1 standard deviation over the past 1000 years) served as a dominant control on Indian monsoon fluctuations during that period.”
“We can anticipate that the monsoon will intensify alongside further Arctic warming, and the difference in precipitation between intense and weak monsoon years will also likely change,” Vikash Kumar at NCPOR’s Past Climate and Ocean Studies (PCOS) division told Mongabay-India.
Faced with the brevity of instrumental weather records from the Arctic (60–100 years), Kumar and colleagues pulled out a 51 cm-long sediment sample from the seafloor at Kongsfjorden, an icy archipelago in Svalbard in the Arctic, to extend the time series for sea conditions 1000 years back in time.
They collected the samples during the Kongsfjorden-Rijpfjorden Cruise in 2014 onboard the research vessel Lance. Back at NCPOR, they looked at the materials trapped in the sediment core. Approximately 2 per cent of the sediment’s weight consisted of marine and land-transported organic matter.
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The Arctic’s influence on the short-term variability of the Indian monsoon may become more significant as the region experiences further warming. Our study supports this idea.
Vikash Kumar, researcher, National Centre for Polar and Ocean Research-Past Climate and Ocean Studies
Kumar and colleagues analysed the elemental and isotopic compositions of these materials in the lab and measured specific biogeochemical parameters, to reconstruct the region’s climate history for the past 1000 years (1107 to 1967).
“Presently, the Indian monsoon’s year-to-year variations are primarily driven by tropical factors. However, the Arctic’s influence on the short-term variability of the Indian monsoon may become more significant as the region experiences further warming. Our study supports this idea,” Kumar adds.
Warm/cold Arctic spells most likely modified the temperature profile of the Tibetan Plateau. The Plateau is an elevated heat source to the atmosphere because of its height and can influence monsoons by influencing the prevailing North-South temperature difference that exists in many forms during the monsoon- such as the land-sea temperature contrast. Both natural and anthropogenic factors influenced the warm and cold spells, they said.
“In my understanding, this is for the first time such a teleconnection pattern between the Arctic climate and Indian monsoon using proxies (indirect measurements) is established,” monsoon researcher Madhavan Rajeevan and former secretary, the Ministry of Earth Sciences told Mongabay-India.
Rajeevan was not associated with the study. He adds that while the relationship between the Arctic climate and Indian monsoon is not a surprise because recent observations suggest a possible linkage of Arctic climate to the Indian monsoon through Arctic Oscillation (atmospheric circulation pattern over the mid-to-high latitudes of the Northern Hemisphere), the current study claims that this relationship exists in the past 1000 years record.
“There are some uncertainties involved in this study (as expected from a paleoclimate study). Nevertheless, this study is very interesting and could encourage more studies using observations and models (especially simulating past paleo climates),” adds Rajeevan.
In a recent paper, researchers at the University of Gothenburg argue that the rate of warming will be much faster than projected but “climate models used by the UN’s IPCC and others to project climate change are not accurately reflecting what the Arctic’s future will be.”
Why the Arctic is important to climate studies
The frigid Arctic is a key indicator of the ongoing shifts in Earth’s climate because it is warming two to three times faster than the global average and losing its sea ice cover.
Svalbard archipelago’s climate sensitivity stems from its setting – it sits along contrasting ocean and air conditions. This group of islands, where samples for the study were collected, is close to the Fram Strait, a deep water channel connecting the Arctic with the Atlantic (Greenland). Exchange of mass, heat, and salt occurs via the channel between Svalbard and Greenland. For example, warm waters flow into the Arctic through this gateway.
“The other reason why Svalbard is of interest to climate and related interdisciplinary researchers is its glacial-marine settings which results in steep gradients (change) in physical and biogeochemical parameters between the glacier head and the oceanic mouth,” explained Kumar of NCPOR.
“Therefore, under climatic stress, changes in glacial discharge and marine influx to the fjord alter these gradients which gets recorded as signals of climate change in core sediments. On top of that, Western Svalbard fjords have high sediment accumulation rates, which means better resolution of reconstructed climate data from these settings.”
The study site, Svalbard and adjoining areas, are a “hotspot within this larger hotspot.”
“To put these rapid modern changes in perspective, it is important to understand their behaviour in the past too. Also, while climate change in the Arctic will continue to remain more spectacular than any other place, other regions will not remain untouched by the rapidly changing Arctic,” said Kumar.
The Arctic is one of the batteries feeding the variations in Indian monsoons, over 7000 kilometres away. In a 2018 study, Vikash Kumar and colleagues showed accelerated glacial melting at Kongsfjorden post-1970s. Changes in remote Arctic such as glacial and sea ice melting, affect Indian monsoons as they contribute to its year-to-year variability that translates into devastating floods and droughts.
“So, it is important that we document and understand past Arctic changes and investigate their pre-instrumental record global connections and ramifications to be better informed for what may come with future Arctic changes,” he said, underscoring that despite being a climate-sensitive hotspot, Svalbard and its surrounding regions are underrepresented in the existing network of Arctic climate proxy archives (indirect measurements).
The paleo interval of the past 1000 years is a good analogue of modern climate conditions.
“The only significant difference between the last millennium and the present is that we humans have pumped a lot of carbon dioxide into the atmosphere in the last 150 years. The knowledge we acquire from studying the climate dynamics of the last millennium offers greater relevance to future climate trends compared to other periods in our geological history.”
“Nonetheless, this does not imply that other paleo intervals lack importance. For instance, the Mid-Pliocene Warm Period, which spans from around 3.3 to 3 million years ago, is also regarded as an ideal analogue for contemporary climate conditions,” added Kumar.
This story was published with permission from Mongabay.com.
